The present invention relates to machines for coating granular articles, such as pharmaceutical or confectionery products, with an outer layer.
More precisely, the invention relates to a device for moving and orienting the spraying nozzles in a coating pan of a machine for coating granular articles.
Currently, articles to be treated are coated in machines including a rotating drum, called coating pan, inside which the articles are introduced.
The coating pan is equipped with perforated hollow bodies, which extend from a manifold coaxial with the rotating drum, and which are immersed in the moving mass of articles to be treated.
A suitable liquid mixture is sprayed on the articles through nozzles, so as to form a protective coating.
Afterwards, a flow of hot air is sent into the articles mass, so as to dry the coating layer.
According to another use of the above mentioned machine, neutral granules are coated with mixtures of active principles and excipients, so as to form e.g. controlled release medicine pellets.
In this case, a predetermined quantity of neutral granules are introduced into the coating pan, so as to be covered, with help of a suitable binder, with layers of mixed powders containing active principles, and excipients.
The binder is introduced into the rotating drum by the spraying nozzles.
During the drum rotation, the appearance of the mass of granular articles changes in relation to different working parameters, e.g. rotation speed and physical characteristics of the articles, generally with the free surface inclined with respect to a horizontal plane.
Therefore, adjusting the position of the spraying nozzles correspondingly to the articles position is a problem that is encountered.
Actually, it is known that best results are obtained when the spraying nozzles are oriented substantially perpendicular to the free surface of the mass of the articles being coated, and at a predetermined distance therefrom.
It is also to be noted that during the production cycle, the volume of the granular articles changes, usually increases, due to the coating layer which settles thereon.
Consequently, the position of the spraying nozzles must be changed in relation to the changing position of the free surface of the granular articles.
In known machines, the position of the spraying nozzles can usually be adjusted manually, with the machine stopped, by acting inside the coating pan or after having removed the nozzles group therefrom.
It is obvious that such manual adjustment is not only difficult, but does not allow to intervene during the articles coating process.
This reduces considerably the efficiency of the coating process and does not allow to obtain best results in different situations.
The object of the present invention is to overcome the above problem by proposing a device which allows to move and locate the spraying nozzles by acting from outside the coating pan and during the granular articles coating process.
Another object of the present invention is to propose a device, which is very versatile in relation to the kind of liquid substance to be sprayed, and in particular, which can be used either for coating pharmaceutical or confectionery products with an outer protective layer, or coating the neutral granules with mixtures of active principles and excipients to obtain e.g. pharmaceutical pellets.
A further object of the present invention is to propose a device, whose construction is very simple and functional.
The above mentioned objects are obtained, in accordance with the claims, by a device for moving and orienting spraying nozzles in a coating pan, the coating pan including:
a rotating drum rotated on a first rotation axis for mixing a predetermined mass of articles being coated, said mass of article defining a free surface; and
a group of spraying nozzles situated inside said rotating drum for spraying a liquid mixture for coating said articles;
said device being characterized by:
a bar supported inside said rotating drum and protruding partially outside said rotating drum;
a support frame, fastened to said bar and located inside said rotating drum;
a shaft rotatably supported by said support frame, said shaft being free to rotate on a second rotation axis parallel to said first rotation axis of said rotating drum;
a plurality of spraying nozzles carried, arranged in a line, by said shaft at a selected distance from said mass of articles being treated with a selected orientation with respect to said free surface of the mass of articles;
a positioning member having a lever mechanism connected to said shaft for changing inclination of said spraying nozzles and maintaining constant the orientation of said spraying nozzles with respect to said free surface of the mass of articles;
said bar being rotated to adjust said distance between said spraying nozzles and said free surface of said mass of articles being treated.